power inverter 500w won't start my laptop

I have an Acer laptop with AC adapter input 100~240V~ 1.6A 50-60Hz
I just bought a small truck battery to be use when power goes down (it happen very frequently in my place)

I also bought a power inverter which state 500W and 220V.

But the problem is, when I plugged in my laptop adapter or any other laptop adapters, it shut down automatically. But when I plugged in desk lamp, or charger several handphones at a time, it worked perfectly.

What is the problem actually? Can anyone help me with some solutions or suggestions?

It sounds like the waveform that it is outputting is not suitable for the laptop charger, either that or it cannot supply enough power based on the fact that it is the inverter shutting down. I just had a look at my acer laptop power brick and it takes 100-240v ~ 1.5A. So, you are at the limits of the power that the inverter is able to supply.

"This is a 300 volt-amp (VA) 12-to-240 volt inverter of slightly elderly design, with a not-so-great surge power rating - the amount of power it can deliver for a brief moment.

Watts may equal volts times amps, but only for DC circuits, or AC circuits running purely resistive loads, like heaters or incandescent lights. Computers and monitors aren't resistive loads. Technically speaking, they have a pretty nasty "power factor". A 300VA inverter can be expected to run only about 210 watts worth of PC gear; maybe even less. For more on this as it applies to computer UPSes, check out APC's PDF format white paper on the subject, here.

Just because a computer has a 300 watt PSU, though, doesn't mean it needs a 430VA inverter. It'll only need that if it fully loads every one of its PSU's output rails, which it almost definitely doesn't.

These days, you can get a 300VA inverter with a 900VA surge rating and better than 90% efficiency for about $AU160 - Jaycar have one, MI-5062, at that price. For less than twice the money, you can get a 600VA continuous, 1500VA surge inverter, which is enough to run pretty much any PC, and its monitor.

Surge rating matters, because many devices draw a lot more current on startup than they do when they're running. Laser printers and refrigerators, for instance, have such huge startup current demands that you need an apparently massively over-rated inverter if you want to run them. Computers aren't that bad, but CRT monitors can still be a problem.

The computer I powered from this rig is a humble Celeron box with a 15 inch monitor. The PC without monitor draws a peak current of about 8.5 amps from the battery, through the inverter, on startup. Then it settles to less than six amps.

The monitor's degauss circuit, though, draws more than the peak power capacity of the inverter.

Since practically all CRTs automatically degauss when they're powered up, that's a problem. Another 15 incher I tried just pegged the needle on my ammeter for a moment when turned on, and then sat there in standby mode.

Fortunately, the old Mitac monitor in the picture can still start up when it tries to degauss itself and fails. It just draws a nice steady eight amps, with no scary surge. So the PC with monitor has a peak draw of a bit less than the inverter's constant output capacity, and then settles down to about 70% of capacity.

Note: If you don't know how thick a wire to use to carry, say, 20 amps (to give a decent safety margin), that's a good sign that you're not quite ready for this project.

The solution to the monitor surge problem, of course, is either to use a more modern inverter with a big surge rating, or to use a lower power monitor, like an LCD screen. 15 inch LCDs (which have more screen area than a "15 inch" CRT) draw less than 40 watts and have no startup surge to speak of. So they're excellent candidates for "alternative power" applications.

Inverter waveforms

The "waveform" of an inverter is how the inverter's output voltage changes as it goes through its positive/negative alternating-current cycles. The rate of oscillation for all Australian 220/240 volt inverters should be the same 50 Hertz (cycles per second) as ordinary mains power in this country, but the voltage-versus-time graph of an inverter's output can be quite different from that of mains power.

If, for instance, the voltage rises practically instantly to full positive, holds there for half a cycle, then drops practically instantly to full negative for the other half-cycle, then you're looking at a "square wave".

Normal mains power alternates in a smooth sine wave - well, it does when it's not being polluted by spikes and sags and surges, anyway. This sinusoidal waveform, shown in green in this picture, is only accurately imitated by more expensive "sine wave" inverters. You can buy UPSes that have sine wave inverters - you're looking at maybe $AU900 for a 750VA line interactive one. You can buy sine wave inverters as separate items, too.

PCs don't need them, though. They'll work fine on modified square wave power - that's the red waveform in the picture. Inverters that output this waveform are cheaper than sine wave units.

Most AC motors - power tools, for instance - will run OK from modified square wave power as well, but they're likely to draw about 20% more power than you'd expect, and may buzz annoyingly. Things with circuitry that relies on clean sine wave power - electric clocks, bread makers, some battery chargers, the "shaded pole" motors used by ceiling fans - are likely to misbehave.

The blue waveform in the picture, by the way, is a plain square wave. It's pretty hard to find plain square wave inverters any more. Which is good, because you probably don't want one. They can run some, but not all, motors, and they're fine with incandescent lights. But even computer power supplies aren't guaranteed to work properly on this exceedingly "dirty" power."

"Depending on the psu in your computer, it might or might not like the modified sine wave.
My laptop transformer is happy with a modified wave but my mates isn't and he had to get a new psu.
So you're really looking to get a pure sine wave inverter if you want guaranteed reliability."

car/truck batteries aren't meant for sustained power draw. They give a lot of power in short bursts but their charge doesn't last very long. This is why most people with rv's/trailers use 6V batteries in series (go kart/golf cart batteries) as they're designed for sustained draw rather than short bursts of a ton of power.

rather than a "wrong power type" issue I think your battery simply doesn't have the juice for the sustained draw of a laptop anymore. Fully charged it may run it for a bit, but then it'll shut down again.

Really I think you're barking up the wrong tree here. A ups would work far better and give you several hours of plugged in use after the power goes out. Once the UPS drains then you're on battery power on the laptop until it wears out. With a decent UPS and a decent laptop battery (might want to upgrade it to an extended life model) you'll be able to get 12-15 hours or more of usage without being messy/bulky.

car/truck batteries aren't meant for sustained power draw. They give a lot of power in short bursts but their charge doesn't last very long. This is why most people with rv's/trailers use 6V batteries in series (go kart/golf cart batteries) as they're designed for sustained draw rather than short bursts of a ton of power.

rather than a "wrong power type" issue I think your battery simply doesn't have the juice for the sustained draw of a laptop anymore. Fully charged it may run it for a bit, but then it'll shut down again.

Really I think you're barking up the wrong tree here. A ups would work far better and give you several hours of plugged in use after the power goes out. Once the UPS drains then you're on battery power on the laptop until it wears out. With a decent UPS and a decent laptop battery (might want to upgrade it to an extended life model) you'll be able to get 12-15 hours or more of usage without being messy/bulky.

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That isn't really true. While it is true that standard car batteries aren't designed to supply a current for as long as something like a deep cycle battery, they definitely can supply a sustained amount of power. Have you ever left your lights on? They'll stay on for a good long while.

In the OP's case I normally I'd doubt the laptop is overloading the inverter since the laptop is only going to draw ~160w max. However, that isn't to say that the inverter isn't horribly overrated, being a seemingly generic POS inverter. I've seen generic made-in-china inverters rated for some huge power rating "peak" but really they couldn't handle that at all and they wouldn't drive anything more than 100w. So plugging a lamp into them would work fine with a 60w bulb, but try powering much more than that and they'd shutdown.

The issue could also be the waveform of the inverter, if it isn't a true sine wave it could cause problems too. However, usually that caused the laptop charger to not work, it doesn't cause the inverter to shut down.

That isn't really true. While it is true that standard car batteries aren't designed to supply a current for as long as something like a deep cycle battery, they definitely can supply a sustained amount of power. Have you ever left your lights on? They'll stay on for a good long while.

In the OP's case I normally I'd doubt the laptop is overloading the inverter since the laptop is only going to draw ~160w max. However, that isn't to say that the inverter isn't horribly overrated, being a seemingly generic POS inverter. I've seen generic made-in-china inverters rated for some huge power rating "peak" but really they couldn't handle that at all and they wouldn't drive anything more than 100w. So plugging a lamp into them would work fine with a 60w bulb, but try powering much more than that and they'd shutdown.

The issue could also be the waveform of the inverter, if it isn't a true sine wave it could cause problems too. However, usually that caused the laptop charger to not work, it doesn't cause the inverter to shut down.

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while the inverter could be bad, it absolutely is true that car batteries aren't designed for sustained draw. This is one of the reasons why they're rated in cold cranking amps rather than amp hours. (the other obvious reason being we want to match the battery supply strength to the starter requirements). Leaving the lights on drains the battery rather quickly actually as many who couldn't start their cars after they've done so can attest to.

Even still the OP is essentially taking the long way around to a UPS, something that's already designed for what he's wanting to do.

The laptop power supply (since it is active PFC due to support for a wide voltage range) could be "rejecting" the waveform and/or causing an amount of in-rush current that the power inverter is incapable of handling. I've heard of certain computer power supplies rejecting UPS units as well, though all of the active PFC power supplies I have tried with an old Ativa AT-BU1200 work fine besides the terrible resonance noise caused by the square wave AC output.

while the inverter could be bad, it absolutely is true that car batteries aren't designed for sustained draw. This is one of the reasons why they're rated in cold cranking amps rather than amp hours. (the other obvious reason being we want to match the battery supply strength to the starter requirements). Leaving the lights on drains the battery rather quickly actually as many who couldn't start their cars after they've done so can attest to.

Even still the OP is essentially taking the long way around to a UPS, something that's already designed for what he's wanting to do.

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I'm not saying they are designed for sustained draw, I'm saying they aren't incapable of it. They are actually very good at it. In fact, they are almost identical to the batteries used in UPSes, they are both just lead-acid batteries, lead plates in a Sulfuric acid solution. The only difference is UPS batteries are sealed so they don't vent dangerous gasses indoors(instead they bulge), and the plates are designed slightly differently to allow UPS batteries(or other forms of deep cycle batteries) to not be damaged by a deep discharge, while the plates in a car battery are designed to allow higher current draw. And the only real difference in performance between the two under small loads is that a car battery can be damaged by a deep discharge. The only affect how fast a battery is drained has on its capacity would be Peukert's Law, but that actually says the opposite of what you say. It states the faster you discharge a lead-acid battery, the lower the capacity appears. It is some complex formula, but that is basically what it says. This is due to the way the chemical reaction happens. If you discharge a lead-acid battery too fast, the chemical reaction that creates the electricity will not happen evenly over the plates. Instead, the area of the plates closest to the terminals will react, while the area further away will have no reaction.

Leaving the lights on takes hours to drain the battery, in fact in my car with a modern batter I've left the parking lights on overnight and still had enough juice in the battery to start the car the next morning 10 hours later. If car batteries were incapable of providing sustained low current power then the dome light in the car, or any of the other relative low power draw items wouldn't work, but they do.

I've even used car batteries as replacement for UPS batteries. And the car battery lasted longer than the original UPS battery. In the end car batteries are still just batteries. And they hold a shitload of power. And that power can either be drained very quickly by starting a car, or very slowly by running a low current draw from it. The battery isn't going to just not work because there isn't enough current being drawn from it, it doesn't work that way.